1. Field of the Invention
This invention is related to an improved powder coating composition and, in particular, to an automotive powder primer surfacer exhibiting substantially improved corrosion resistance under a powder topcoat.
2. Description of the Prior Art
Primers are widely used in preparation for the topcoating of metal or steel substrates to form a smooth surface over which the topcoat is applied. Powder primers, which contain no solvent, have gained in popularity since they are compatible with the current environmental emphasis on solvent reductions. For a description of a representative epoxy-resin powder primer composition, see U.S. Pat. No. 4,251,426, issued Feb. 17, 1981, to McClure and Victorius.
However, in utilizing both a powder primer and a powder topcoat, problems with corrosion resistance have been encountered which are not encountered when using topcoat coating compositions involving traditional lacquers and enamels, or even aqueous and high solids technologies. The present invention provides for a powder primer which exhibits unexpectedly improved corrosion resistance when utilized under a powder topcoat.